Method and device for determining chlorine dioxide in aqueous solutions

Abstract

A test method and device are described for quantitatively determining the presence and concentration of chlorine dioxide in aqueous solution, which may contain chlorine. Contacting the aqueous solution containing chlorine dioxide with a test strip in accordance with the invention produces a color change in proportion to the concentration of the chlorine dioxide. The invention has particular utility in determining the presence of chlorine dioxide in water containing chlorine such as municipal water.

What is claimed:  
     
         1 . A method for determining the concentration of chlorine dioxide in aqueous solution containing chlorine, the method comprising: 
 A. Contacting an aqueous test solution containing chlorine dioxide with a reagent composition comprising: 
 a. A chromogenic indicator capable of reacting with chlorine dioxide present in said aqueous test solution to give a color response proportional to the concentration of said chlorine dioxide;  
 b. A buffer to maintain the test solution and composition at a pH of 5 to 7;  
 c. 0.1 to 2% surfactant;  
 d. 0.1 to 2% of a stabilizing polymer; and  
 e. 0.05 to 0.2% of an amphoteric component that provides dipolar ions or zwitterions or simple amine or a salt of ammonia in said aqueous solution to prevent interference by chlorine in the reaction of said chromogenic indicator with said chlorine dioxide;  
   B. Comparing said color response obtained to color responses obtained from known standardized aqueous solutions containing chlorine dioxide and translating such comparisions to the concentration of chlorine dioxide in the test solution.    
     
     
         2 . The method of  claim 1  wherein said chromogenic indicator is a redox indicator.  
     
     
         3 . The method of  claim 2  wherein said indicator is a heterocyclic azine or benzidine.  
     
     
         4 . The method of  claim 1  wherein said amphoteric component is an amino acid.  
     
     
         5 . The method of  claim 4  wherein said amino acid is one or more components selected from glycine, alanine, leucine, proline and histidine.  
     
     
         6 . The method of  claim 1  wherein the reagent composition is incorporated onto a fluid absorbent matrix material and the matrix is contacted with the test solution sample.  
     
     
         7 . The method of  claim 6  wherein the fluid absorbent matrix material is a cellulose based paper, glass fiber or polyester material.  
     
     
         8 . The method of  claim 3  wherein said indicator is syringaldazine.  
     
     
         9 . A method for determining the concentration of chlorine dioxide in aqueous solution comprising: 
 A. contacting a test solution sample with a reagent composition deposited on an absorbent matrix material comprising a) a chromogenic indicator material selected from the group consisting of (1) a compound having the formula                          where R and R′ are selected from the group consisting of hydroxy and amino groups and X,X′, Y and Y′ are selected from the group consisting of hydrogen, hydroxy, methyl, methoxy, ethyl and ethoxy groups; b) a buffer to maintain the test composition and test solution sample in a pH range of about from 5 to 7; c) 0.05 to 0.2% of an amphoteric amino acid or amine or a salt of ammonia that prevents chlorine in the test solution from interfering with color response by said chromogenic indicator material. d) 0.1 to 2% surfactant and; e) 0.1 to 2% of a stabilizing polymer, and    B. comparing the color response obtained to color responses from standardized solutions of chlorine dioxide and translating such comparison to the amount of chlorine dioxide in the test solution.    
     
     
         10 . A test device for the determination of chlorine dioxide in aqueous solutions comprising a matrix material incorporated with the dried residue of a test composition comprising: 
 A. A chromogenic indicator capable of reacting with chlorine dioxide to give a color change;    B. A buffer to maintain the test solution and composition at pH of 5 to 7;    C. 0.05 to 0.2% of an amphoteric component or amine or a salt of ammonia that prevents interference by chlorine in the solution with color response by said chromogenic indicators.    D. 0.1 to 2.0% surfactant E. 0.1 to 2.0% of a stabilizing polymer    
     
     
         11 . The test device of  claim 10  wherein said chromogenic indicator is a heterocyclic azine or benzidine.  
     
     
         12 . The test device of  claim 11  wherein said chromogenic indicator is syringaldazine.  
     
     
         13 . The test device of  claim 10  wherein said amphoteric component is an amino acid.  
     
     
         14 . The test device of  claim 10  wherein said matrix material is absorbent cellulosic paper.  
     
     
         15 . The test device of  claim 13  wherein said amino acid is one or more components selected from glycine, alanine, leucine, proline and histidine.